Honeycomb structures having a catalyst component loaded thereon have been used in an exhaust gas purifier of a heat engine (e.g. an internal combustion engine) or a burner (e.g. a boiler), a reforming unit of a liquid fuel or a gaseous fuel, and the like. It is known that honeycomb structures are also used as a filter for capturing and removing the particulate matter contained in a dust-containing fluid such as exhaust gas emitted from a diesel engine.
The honeycomb structures used for such purposes have had problems; for example, they undergo rapid temperature change or local heating by the action of an exhaust gas, an uneven temperature distribution appears therein, resultantly they come to have cracks. Particularly when they were used as a filter for capturing the particulate matter contained in the exhaust gas emitted from a diesel engine, cracks appeared easily because the carbon fine particles accumulated on the filter must be burnt for removal and it inevitably causes local heating to high temperatures and easily generates a large thermal stress. In this case, the thermal stress is generated because the uneven temperature distribution allows different portions of the honeycomb structure to have different thermal expansion deformations and resultantly each portion is restricted by each other and is unable to make free deformation.
To reduce the stress, there was proposed, in, for example, JP-A-59-199586, a honeycomb structure having a large number of through-holes each surrounded by partition walls, wherein partition wall areas having at least one slit are formed at given portions of the honeycomb structure almost uniformly.
In this proposal, small slits are distributed uniformly in a honeycomb structure, thereby the rigidity of the total honeycomb structure is reduced and the freedom of deformation is increased, therefore an effect of stress reduction is achieved. However, the degree of an increase in the freedom of deformation is insufficient; therefore, the above proposal for stress reduction was insufficient for a honeycomb structure used under severe conditions where the unevenness of temperature distribution becomes larger.
In view of the above-mentioned problems of the prior art, the present invention aims at providing a honeycomb structure which gives no cracks by thermal stress during use and which is superior in durability.